Samarium(II) iodide
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| Samarium(II) iodide | |
|---|---|
| Image:Samarium(II) iodide.jpg | |
| General | |
| Other names | Samarium diiodide |
| Molecular formula | SmI2 |
| Molar mass | 404.16 g/mol |
| Appearance | green solid |
| CAS number | [32248-43-4] |
| Properties | |
| Density and phase | ? g/cm3, ? |
| Solubility in water | ? g/100 ml (?? °C) |
| Melting point | 520 °C |
| Boiling point | ? °C |
| Thermodynamic data | |
| Standard enthalpy of formation ΔfH°solid |
? kJ/mol |
| Standard molar entropy S°solid |
? J.K−1.mol−1 |
| Safety data | |
| EU classification | not listed |
| NFPA 704 | |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | Samarium(II) chloride Samarium(II) bromide |
| Other cations | Samarium(III) iodide Europium(II) iodide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
Samarium(II) iodide (SmI2) is a green solid composed of samarium and iodine, with a melting point of 520 °C [1]. It can be formed by high temperature decomposition of SmI3 (the more stable iodide), but a convenient lab preparation is to react Sm powder with 1,2-diiodoethane in anhydrous THF [2], or CH2I2 may also be used [4]. Samarium(II) iodide is a powerful reducing agent - for example it rapidly reduces water to hydrogen. It is available commercially as a dark blue 0.1 M solution in THF.
Samarium(II)iodide has become a popular reagent for carbon-carbon bond formation, for example in a Barbier reaction (similar to the Grignard reaction) between a ketone and an alkyl iodide to form a tertiary alcohol [3]:
RI + R'COR → R(R')C(OH)R
Typical reaction conditions use SmI2 in THF in the presence of catalytic NiI2.
Esters react similarly (adding two R groups), but aldehydes give by-products. The reaction is convenient is that it is often very rapid (5 minutes or less in the cold). Also, it can be monitored by the color change that occurs as the dark blue color of SmI2 in THF discharges to a light yellow once the reaction has occurred. The picture shows the dark colour disappearing immediately upon contact with the Barbier reaction mixture.
Work-up is with dilute hydrochloric acid, and the samarium is removed as aqueous Sm3+.
The applications of SmI2 have been reviewed [4].
[edit] References
- Chemistry of the Elements, NN Greenwood & A Earnshaw, Pergamon Press.
- P. Girard, J. L. Namy, H. B. Kagan J. Am. Chem. Soc. 1980, 102, 2693-8. First Page
- Synlett, 1996, 633-4.
- J. Chem. Soc., Perkin Trans. I, 2001, 2727-2751.
